The present invention concerns a system, in particular for timing races, and more particularly such a system including an optical device installed in a fixed station in the extension of a line across which objects or persons pass for projecting an image of such line onto a photosensitive sensor. The invention also concerns a method for adjusting the alignment of such a system with a line across which objects or persons pass such as a finish line of a race.
European Patent Document No. EP-A-0 207 675 discloses a system for determining the times separating the passing of competitors across a line of a race or a reference line substantially perpendicular to their trajectory. This system includes a camera, an image storage and processing device, a control box and a monitoring screen. The camera includes an optical unit with which is associated a photosensitive sensor on which the image of the reference line is intended to be projected. The optical unit comprises a conventional optical lens and the photosensitive sensor is formed of a bar, comprising a plurality of juxtaposed pixels in a single column, generally designated a CCD (Charged Coupled Device) bar.
In order to operate satisfactorily, the camera has to be installed in a fixed station in the extension of the reference line and perpendicular thereto. More particularly, the reference line must be in perfect alignment with the CCD bar of the camera.
Such alignment is generally achieved in two steps.
According to a first step implemented at the factory, the CCD bar is aligned once and for all with the camera optical device on an optical bench. During this operation, the CCD bar is moved with respect to the optical unit in order to bring it into superposition with a line of sight of an eyepiece mounted on the camera optical unit via different screw adjustment mechanisms. Once this adjustment is performed, the CCD bar is secured in this position via mechanical means such as screws.
According to a second step, the CCD bar is aligned with the reference line via the eyepiece upon each installation of the camera on site. For this purpose, the optical unit further includes a mirror swinging between a first position called the operating position, in which the plane of the mirror is clear of the optical path connecting the CCD bar to the lens and a second position, called the adjusting position, in which the mirror is placed on said optical path and reflects the image perceived by the lens, in this case the image of the reference line, onto the eyepiece. In order to perform the alignment of the CCD bar with the reference line, it is thus necessary to place the mirror in the adjusting position, then to move the camera, which has previously been fixed to a conventional adjustment tripod, while watching the image of the reference line in the eyepiece until such image is superposed with said line of sight of the eyepiece. Once this latter adjustment has been performed, the tripod is fixed in this position via conventional mechanical means and the shooting can begin.
This system has different drawbacks due, in particular, to the fact that it requires the use of adjustment mechanisms including numerous parts which are complicated to machine which makes manufacturing laborious and significantly increases the cost price of the camera. The limited reliability of the system, due to the numerous mechanical parts of which it is formed, should also be mentioned in this regard.
Moreover, the adjustments required by the camera during the assembly thereof at the factory are long and intricate. Further, in the event of shocks or vibrations, the mechanical parts of the eyepiece adjustment device can become bent and bring the reticule of the eypiece out of alignment with respect to the CCD bar.
A main object of the invention is thus to overcome the drawbacks of the aforementioned prior art by providing a system including a camera which includes a simple inexpensive device allowing accurate adjustment of the alignment of a photosensitive sensor of the CCD bar type with a line across which objects or persons pass such as a finish line of a race.
The invention therefore concerns a system able to be installed in the extension of a line across which at least one object or person passes (hereinafter xe2x80x9ccrossing linexe2x80x9d), such as a finish line of a race, said system including:
an optical device for projecting an image of this line onto a photosensitive sensor capable of providing electric signals representative of the image projected by the optical device and captured by said sensor, called the image signal,
means for processing said image signal,
display means provided for displaying on a screen an image representative of said image signal, called the video image, connected to said processing means. This system is characterised in that said sensor is formed of a pixel matrix,
in that it is provided with means for generating a signal forming a reticule which is displayed on said screen and which is superposed onto the video image, and
in that it further includes means for extracting, from said image signal which they receive as input, electric signals originating from a column of pixels of the matrix which corresponds to the position of the reticule on the screen and for providing a column signal as output.
As a result of these features, the complicated operation and mechanical structure of the optical unit of the systems of the prior art are replaced by a single sensor, which allows both the accuracy of alignment of the system and the reliability thereof to be increased while reducing the cost price thereof.
According to an advantageous feature of the invention, the reticule is associated with control means via a comparator circuit which receives as input the image signal and a reference signal originating from the control means and provides as output a control signal, and the reticule can be moved across the image in response to the control signal.
Thus, one can for example select, by means of an electronic cursor, the CCD column which corresponds to the reference line which one can see on a monitoring screen.
According to a preferred embodiment of the invention, the system further includes means for switching the image signal either to the processing means, or to the extraction means, thereby switching the system into respectively a spatial or temporal operating mode.
These switching means have, in particular, the advantage of allowing the positioning of the system to be checked easily at any time simply by switching the system from the temporal mode to the spatial mode. In other words, the system can be passed from the mode in which it uses only one single pixel column to acquire the data representing the image given at each moment of the crossing line, and for example to process such data in conformity with the description given in European Patent No. EP 0 402 749, which is incorporated herein by reference, to the mode in which the sensor is used conventionally as a video image sensor with a sweep frequency which depends only on the standard used, for example PAL, NTSC or suchlike.
The invention also concerns a method for adjusting the alignment of a system with a line across which objects or person pass, the system including an optical device having an optical axis, the device being capable of projecting an image of this line onto a photosensitive sensor formed of a matrix of pixels capable of providing electric signals representative of the projected image received by said sensor, called the image signal, means for processing said image signal, display means provided for displaying an image representative of said image signal, called the video image, on a screen, said display means being connected to the processing means, characterised in that it includes the steps consisting in:
(a) placing the system in the extension of said crossing line so that the axis of its optical device is substantially directed onto said line,
(b) reading at a first determined frequency the electric signal provided by the pixels situated in several columns of the matrix forming the sensor to generate on the screen said video image including in particular the image of said crossing line;
(c) generating a signal forming a reticule which is displayed on said screen and which is superposed onto a portion of the video image;
(d) superposing the reticule onto said image of said crossing line in the video image; and
(e) selecting the pixel column of the sensor which corresponds to the reticule.
It will be noted that according to the method of the invention, the alignment of the system can be performed by moving, for example via an electronic control, a reticule onto a video image in order to superpose the reticule onto the image of the crossing line appearing on the screen. Thus, adjustment of the alignment is simplified in particular in that the use of mechano-optical mechanisms is completely omitted.
According to an advantageous implementation of the invention, the method described hereinbefore can be completed by the steps of:
(f) reading at a second determined frequency, the electric signal provided by the selected pixel column, called the column signal, which corresponds to the image intensity profile of said line at a given moment; and
(g) providing said column signal to exploitation means.
Thus, once the alignment steps have been performed, the alignment method of the invention can be completed in simple manner to offer other possibilities for exploiting the method such as timing races.
Other features and advantages of the invention will appear more clearly upon reading the following description of an embodiment of the invention given purely by way of illustrative and non limiting example, this description being given in conjunction with the annexed figures, in which: